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# Character replacement after removing duplicates from a string

• Difficulty Level : Basic
• Last Updated : 24 Nov, 2022

Given a string. The task is to replace each character of the minimized string with a character present at the index ‘IND‘ of the original string. The minimized string is the string obtained by removing all duplicates from the original string keeping the order of elements the same.

IND for any index in the minimized string is calculated as:

IND = (square of ascii value of minimized string character) % (length of original string)

Examples:

```Input : geeks
Output : sesg
Explanation :   minimized string = geks
length of original string = 5
ascii value of g = 103
IND for g = (103*103) % 5 = 4
replacement character for g = s
character 's' present at index 4 of original string
Similarly,
replacement character for e = e
replacement character for k = s
replacement character for s = g

Input : helloworld
Output : oeoeeoh```

Approach:
Below is the step-by-step algorithm for string minimization:

```    1. Initialize flagchar = {0}
2. for i=0 to str.length()-1
3.     ch = str[i]
4.     if flagchar[ch-97] == 0 then
5.         mstr = mstr + ch
6.         flagchar[ch-97] = 1
7.     End if
8. End of loop
9. return mstr  // minimized string```

Algorithm for character replacement:

```    1. Replace each character of minimized string as described
in the problem statement and example
2. Compute final string ```

Below is the implementation of the above approach:

## C++

 `// C++ program for character replacement` `// after string minimization` `#include ` `using` `namespace` `std;`   `// Function to minimize string` `string minimize(string str)` `{` `    ``string mstr = ``" "``;` `    ``int` `l, i, flagchar = { 0 };` `    ``char` `ch;`   `    ``l = str.length();`   `    ``// duplicate characters are removed` `    ``for` `(i = 0; i < str.length(); i++) {` `        ``ch = str.at(i);`   `        ``// checks if character has previously occurred or not` `        ``// if not then add it to the minimized string 'mstr'` `        ``if` `(flagchar[ch - 97] == 0) {` `            ``mstr = mstr + ch;` `            ``flagchar[ch - 97] = 1;` `        ``}` `    ``}`   `    ``return` `mstr; ``// minimized string` `}`   `// Utility function to print the` `// minimized, replaced string` `void` `replaceMinimizeUtil(string str)` `{` `    ``string minimizedStr, finalStr = ``""``;` `    ``int` `i, index, l;` `    ``char` `ch;` `    ``l = str.length();`   `    ``minimizedStr = minimize(str); ``// minimized string`   `    ``// Creating final string by replacing character` `    ``for` `(i = 0; i < minimizedStr.length(); i++) {` `        ``ch = minimizedStr.at(i);`   `        ``// index calculation` `        ``index = (ch * ch) % l;`   `        ``finalStr = finalStr + str.at(index);` `    ``}`   `    ``cout << ``"Final string: "` `<< finalStr; ``// final string` `}`   `// Driver program` `int` `main()` `{` `    ``string str = ``"geeks"``;`   `    ``replaceMinimizeUtil(str);`   `    ``return` `0;` `}`

## Java

 `// Java program for character replacement` `// after String minimization`   `class` `GFG {` `    ``// Function to minimize String`   `    ``static` `String minimize(String str)` `    ``{` `        ``String mstr = ``" "``;` `        ``int` `l, i, flagchar[] = ``new` `int``[``26``];` `        ``char` `ch;`   `        ``l = str.length();`   `        ``// duplicate characters are removed` `        ``for` `(i = ``0``; i < str.length(); i++) {` `            ``ch = str.charAt(i);`   `            ``// checks if character has previously occurred or not` `            ``// if not then add it to the minimized String 'mstr'` `            ``if` `(flagchar[ch - ``97``] == ``0``) {` `                ``mstr = mstr + ch;` `                ``flagchar[ch - ``97``] = ``1``;` `            ``}` `        ``}`   `        ``return` `mstr; ``// minimized String` `    ``}`   `    ``// Utility function to print the` `    ``// minimized, replaced String` `    ``static` `void` `replaceMinimizeUtil(String str)` `    ``{` `        ``String minimizedStr, finalStr = ``""``;` `        ``int` `i, index, l;` `        ``char` `ch;` `        ``l = str.length();`   `        ``minimizedStr = minimize(str); ``// minimized String`   `        ``// Creating final String by replacing character` `        ``for` `(i = ``0``; i < minimizedStr.length(); i++) {` `            ``ch = minimizedStr.charAt(i);`   `            ``// index calculation` `            ``index = (ch * ch) % l;`   `            ``finalStr = finalStr + str.charAt(index);` `        ``}` `        ``// final String` `        ``System.out.println(``"Final String: "` `+ finalStr);` `    ``}`   `    ``// Driver program` `    ``public` `static` `void` `main(String[] args)` `    ``{` `        ``String str = ``"geeks"``;`   `        ``replaceMinimizeUtil(str);` `    ``}` `}` `// This code is contributed by Rajput-JI`

## Python3

 `# Python3 program for character ` `# replacement after string minimization `   `# Function to minimize string ` `def` `minimize(string): ` ` `  `    ``mstr ``=` `" "` `    ``flagchar ``=` `[``0``] ``*` `26`  `    ``l ``=` `len``(string) ` `    `  `    ``# Duplicate characters are removed ` `    ``for` `i ``in` `range``(``0``, ``len``(string)): ` `     `  `        ``ch ``=` `string[i] ` `        `  `        ``# checks if character has previously occurred or not ` `        ``# if not then add it to the minimized string 'mstr' ` `        ``if` `flagchar[``ord``(ch)``-``97``] ``=``=` `0``: ` `         `  `            ``mstr ``=` `mstr ``+` `ch ` `            ``flagchar[``ord``(ch)``-``97``] ``=` `1` `                 `  `    ``return` `mstr ``# minimized string ` ` `  `# Utility function to print the ` `# minimized, replaced string ` `def` `replaceMinimizeUtil(string): ` ` `  `    ``finalStr ``=` `"" ` `    ``l ``=` `len``(string) ` `    ``minimizedStr ``=` `minimize(string) ``# minimized string ` `    `  `    ``# Creating final string by replacing character ` `    ``for` `i ``in` `range``(``0``, ``len``(minimizedStr)): ` `     `  `        ``ch ``=` `ord``(minimizedStr[i]) ` `        `  `        ``# index calculation ` `        ``index ``=` `(ch ``*` `ch) ``%` `l ` `        ``finalStr ``=` `finalStr ``+` `string[index] ` `    `  `    ``print``(``"Final string:"``, finalStr) ``# final string ` ` `  `# Driver program ` `if` `__name__ ``=``=` `"__main__"``: ` ` `  `    ``string ``=` `"geeks"` `    ``replaceMinimizeUtil(string) `   `# This code is contributed by Rituraj Jain`

## C#

 `// C# program for character replacement` `// after String minimization` `using` `System;`   `class` `GFG {`   `    ``// Function to minimize String` `    ``static` `String minimize(``string` `str)` `    ``{` `        ``string` `mstr = ``" "``;` `        ``int` `l, i;` `        ``int``[] flagchar = ``new` `int``;` `        ``char` `ch;`   `        ``l = str.Length;`   `        ``// duplicate characters are removed` `        ``for` `(i = 0; i < str.Length; i++) {` `            ``ch = str[i];`   `            ``// checks if character has previously` `            ``// occurred or not if not then add it` `            ``// to the minimized String 'mstr'` `            ``if` `(flagchar[ch - 97] == 0) {` `                ``mstr = mstr + ch;` `                ``flagchar[ch - 97] = 1;` `            ``}` `        ``}`   `        ``return` `mstr; ``// minimized String` `    ``}`   `    ``// Utility function to print the` `    ``// minimized, replaced String` `    ``static` `void` `replaceMinimizeUtil(``string` `str)` `    ``{` `        ``string` `minimizedStr, finalStr = ``""``;` `        ``int` `i, index, l;` `        ``char` `ch;` `        ``l = str.Length;`   `        ``minimizedStr = minimize(str); ``// minimized String`   `        ``// Creating final String by` `        ``// replacing character` `        ``for` `(i = 0; i < minimizedStr.Length; i++) {` `            ``ch = minimizedStr[i];`   `            ``// index calculation` `            ``index = (ch * ch) % l;`   `            ``finalStr = finalStr + str[index];` `        ``}`   `        ``// final String` `        ``Console.Write(``"Final String: "` `+ finalStr);` `    ``}`   `    ``// Driver Code` `    ``public` `static` `void` `Main()` `    ``{` `        ``string` `str = ``"geeks"``;`   `        ``replaceMinimizeUtil(str);` `    ``}` `}`   `// This code is contributed` `// by ChitraNayal`

## PHP

 ``

## Javascript

 ``

Output

`Final string: ssesg`

Time Complexity: O(n), where n is the length of the given string.
Auxiliary Space: O(n)

This article is contributed by Ayush Jauhari. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.